Intensifying and fluorescent screen



March 21, 1939. JI EGGERT ET Al. 2,150,966.

INTENSFYING' AND FLUORESCENT SCREEN Filed oct. 19, 1955 John E rf Fritzf Inventors Patented Mar. 21, 1939 l l 2,150,966

INTENSIFYING AND FLUORESCENT SCREEN John Eggert and Fritz Luft, Leipzig,Germany,

assignors to Agfa Ansco Corporation, Bingl hamton, NZX., a corporationof New York Application October 19, 1935, Serial No. 45,780 In GermanyMarch 15, 1933 fi claims. (C1. 25o-so) Our present invention relates toan intensifying binding agent carrying theuoiescent substance oruorescent screen for X-ray work. It is a instead of being incorporatedin a special filter continuation-impart of my co-pending applicalayer. ltion Ser. No. 714,729, filed March 8, 1934 now U. S. l'Furthermoresubstances are known, such as 5 Patent2,076,984. zinc sulfide andsulfides of the alkaline earths, 5

One of its objects is an improved screen of this which luoresce andphosphoresce when struck by kind. Further objects will be seen from thede- X-rays or by daylight. If such substances are tailed specificationfollowing hereafter. used for the manufacture of intensifying screens,

Many intensifying and uorescent screens for these screens must, ofcourse, always be protected useinX-ray work have the disadvantage ofbeing from daylight, thus causing much trouble in 10 phosphorescent,that is to say, the screens not X-ray work. only emit the desiredfluorescent radiation during Now, according to Stokes law, theseluminesthe diagnostic exposure, but also produce after cent rays alwayshave a greater wave length exposure a phosphorescent light at the placesthan the `exciting primary rays. By providing previously struck by theX-rays, so that on the iiuorescent screens with a filter (in the wayabove 15 screens the successively produced phosphorescent referred to,i. e. applying a lter layer by casting and fluorescent pictures becomemixed, a fact or dyeing 'the layer throughout its thickness) which mayrender difficult the interpretation of which absorbs only the excitinglight, and transthe inspected or photographed picture. As mits theluminescent rays completely or in greater known, it is very diicult tofree the luminescent part, the risk that such a screen be excited insubstances used in the manufacture of intensify-1 daylight is greatlydiminished, without the exing screens and fluorescent screens for X-raycitability by X-rays being reduced or the emission work from substancesthat phosphoresce when of the fluorescent rays being materiallyhindered. struckby X-rays. With a screen protected in this manner,therefore,

This phosphorescent light frequently has acolor X-ray work may be donealmost irrespective of g5 different from that of the fluorescent light.By any previous exposure to daylight. the invention the detrimentaleifect caused by In the following table there are given some thephosphorescent substances contained in the materials which are used formanufacturing iniluorescent layer may be eliminated by coatingtensifying or uorescent screens and materials the intensifying screen orthe fluorescent screen which they may contain as impurity. 'Ihere is 30with a lter layer which transmits the fluorescent furthermore indicatedthe fluorescent and phoslight completely or in greater part, but absorbsphorescent light emanated by these materials and the phosphorescentrays. By this expedient the the iilter dye to be used for absorbing thephosufacture of intensifying and fluorescent phorescent light.

Color oi Color of liuc- Main constituent Impurity phospho- Filter dyel'eSCDCG resn Zus activated with Ag.. Mn Dark blue Orange.. Toluidineblue (ci. Schultz Farbstofi'tabellen 7th edition No. 1041) or crystalviolet (hexa- 40 methylparerosaniliue). Do Cu .do Green Rose bengale(ci. Schultz Farbstoiitabellen 7th l edition N o. 889). ZnS activatedwith Cd.. Mn Orangeyeliow,. do Onnge 2N(cf.18)chultz -Farbstofitabelleu7th e ition o. CaW04 ZnSuctivated Blue ,do Rose beugels (et. SchultzFarbstotabellon 7th with Mn. edition N o. 889).

screens for X-ray work is considerably cheapened '"ihe followingexamples illustrate the invenand improved, because on the one hand thecomtion: plicated process of removing the phosphorescent Example 1.-Anintensifying screen for X-ray adm ixtures from the nuorescent substancesis work. consists ofa support, for instance stiff paper, 5g, renderedunnecessary and on the other hand and a uerescent layer, containing as afluorescent y there is a wider choice of uorescent substances substance,zinc sulfide activated with silver. This since those which givefluorescence and also phoslayer is coated with another layer containingas a phorescence substances can be used. If required, lter dyestufcrystal violet in gelatin as a binding the lter dyestu may be addeddirectly to the agent. If the zinc sulfide activated with silver u andiiuorescing with a blue color, contains as usual traces of copper, thescreen will phosphoresce with a green light, which is absorbed by theillter layer containing crystal-violet. The blue iuorescent lightpenetrates the filter layer unweakened.

Example 2.--An intensifying screen containing as an active substancezinc Isulide activated with copper is coated with a green nlter layer ofgelatin dyed with `tartrazine and patent blue. This filter layerprevents the screen from being excited by daylight by absorbing the blue`rays exciting phosphorescence. On the contrary, X- rays which are notabsorbed by such a filter excite a iluorescent radiation. Theyellowishgreen nuorescence light produced is transmitted by the iilterlayer.

The following table indicates some examples of a fluorescent screenwhich may be excited by daylight and the illter dyes tok be used" foravoiding the daylight excitation so that the fluorescent screen isexcited only by X-rays:

l See Schultz Farbstoftabellen 7th edition No. 727. I See SchultzFarbstotabollen 7th edition No. 826. l and i Sec SchultzFarbstoiltabellen 7th edition No. 737. See Schultz Farbstoiltabellen 7thedition No. 189.

Our invention is illustrated in the accompanying drawing in which Fig. 1shows a modication in which the layer containing the fluorescentmaterial is provided with a lter layer for absorbing that part ofdaylightcausing excitation and Fig. 2 shows a-modication in which thelayer containing the fluorescent material is colored throughout by a dyeabsorbing that part of day- Y light causing excitation.

What we claim is: A

1. An intensifying or fluorescent screen for X-ray work mdngomprisesuniformly distributed in a binding agezcxtaa1 fgorescent material Iwhich nuoresces under the uence of daylight and also X-rays and a dyeabsorbing that-.part of daylight causing excitation and permeable forthe fluorescent rays emanating from the iluorescent material onexcitation by X-rays.

2. An intensifying or nuorescent screen for X ray work which comprisesin 'its active layers a iluorescent material which liluoresces underthek oi'rdaylight causing excitation and permeable for the fluorescentrays emanating from the fluores-` cent material on excitation by X-rays.

4. Anintensifying or fluorescent screen for X- ray work which comprisesa layer containing zinc sulde activated with copper and coated on thislayer a filter layer of gelatin, dyed .with'a mixture oi tartrazine andpatent blue.

Y JOHN EGGERT. nu'rz LUM'.

